Microelectromechanical (MEM) safing and arming (safe-arm) devices may be utilized in energetic components comprising pyrotechnic and/or explosive materials. MEM safe-arm devices can function to prevent the un-intentional operation of an energetic component by rendering an explosive train safe (i.e. out-of-line) and, can function to allow an intended operation of an energetic component, by completing an explosive train (i.e. inline). Inertial sensing MEM safe-arm devices can operate to change the state of an explosive train from out-of-line (i.e. unarmed) to inline (i.e. armed) in response to the inertial forces, caused by accelerations representative of an intended operating environment of the component. For example, an inertial sensing MEM safe-arm device can be configured to complete an explosive train by the action of one or more accelerations representative of an expected flight path, trajectory, spin-up, firing or launch of an energetic component. Inertial sensing MEM safe-arm devices can also be configured to maintain an explosive train in an out-of-line state, thereby preventing the arming of an explosive component, if an unexpected or abnormal inertial environment (i.e. acceleration) is sensed. Energetic components that can utilize inertial sensing MEM safe-arm devices can be found in air bag deployment systems, initiators for rocket propellants and boosters, pyrotechnics and, munitions including gun fired, spinning projectiles.
Microelectromechanical (MEM) fabrication technologies, including surface micromachining methods based on integrated circuit (IC) manufacturing (e.g. semiconductor device manufacture), bulk micromachining, focused ion beam (FIB) processing, LIGA (an acronym based on the first letters of the German words for lithography, electroplating and molding) and their combination, can be used to form micro-electromechanical systems (MEMS) microsensors and microactuators, including inertial sensing MEM safe-arm devices. MEM fabrication technologies can provide for batch fabrication of multiple devices, that are fully assembled as-fabricated, requiring little to no post fabrication assembly. Dimensions of structures fabricated by MEM technologies can range from on the order of 0.1 μm, to on the order of a few millimeters, and include silicon, polysilicon, glass, dielectric and metallic structures that are either unsupported (i.e. free standing) or alternatively can be adhered to a substrate, or built up upon a substrate during manufacture. Substrates can comprise ceramics, glass-ceramics, low-temperature co-fireable ceramics (LTCC), quartz, glass, a printed wiring board (e.g. manufactured of polymeric materials including polytetrafluoroethylene, polyimide, epoxy, glass filled epoxy), silicon (e.g. silicon wafers) and metals. Dielectric layers for example, polymeric, silicon-oxide, silicon-nitride, glass and ceramic layers can be applied to the surface of conductive substrates (e.g. metallic and silicon substrates) to electrically isolate individual MEM structures or MEM elements within a structure. Embodiments of the present invention fabricated in MEM technologies, can comprise inertial sensing safe-arm devices that are highly integrated and compact, and are readily insertable into the explosive train of an energetic component.
In the context of the present disclosure, MEM devices are defined to be those devices manufactured using one or more of the MEM fabrication technologies described above, and having dimensions ranging from on the order of 0.1 μm, to on the order of a few millimeters. An explosive train is defined herein as a succession of one or more initiating, igniting, detonating, and explosive (e.g. booster) charges, arranged to cause an energetic material within the explosive train, to combust, explode, or otherwise spontaneously release energy. Elements within an explosive train can include: electrically heated wires, spark gaps, bridge wires, silicon bridgewires (SCBs), reactive initiators (e.g. layered structures of exothermically reacting materials such as aluminum and palladium, and titanium and boron), slappers (e.g. exploding foil initiators), chip slappers, detonators, explosive charges and other energetic materials (i.e. pyrotechnics and fuels). Energetic components include components and devices that comprise energetic materials such as explosives, propellants, fuels, gas generating materials, combustibles, unstable and metastable materials. The energetic materials within an energetic component can be arranged in an explosive train. The path of an explosive train is defined herein to be the path of energy transfer from one element within the explosive train, to another element within the explosive train.